1. Field of the Invention
The present invention relates to an apparatus for simultaneously grinding or polishing end surfaces of a plurality of optical fibers which are connected to respective fiber end devices.
More specifically, the present invention is concerned with an apparatus for simultaneously or independently grinding the end surfaces of different types of optical fibers connected to a variety of types of fiber end devices which are often used at sites where optical fiber cable is laid.
2. Prior Art
TAKAHASHI, one of the inventors of the present invention, has made many proposals in regard to grinding of end surfaces of optical fibers. For instance, the following patents and patent application pertain to grinding apparatuses capable of simultaneously grinding end surfaces of a plurality of optical fibers:
U.S. Pat. No. 4,831,784 PA0 U.S. Pat. No. 4,979,334 PA0 U.S. Pat. No. 5,216,846 PA0 Japanese Patent Laid-Open No. 6-179161; U.S. Ser. No. 08/019,303
POLISHING APPARATUS FOR END SURFACES OF OPTICAL FIBERS PA1 OPTICAL FIBER END SURFACE POLISHING DEVICE PA1 METHOD AND APPARATUS FOR GRINDING FOREMOST END OF FERRULE PA1 APPARATUS FOR GRINDING ENDFACES OF FERRULES TOGETHER WITH OPTICAL FIBERS EACH FIRMLY RECEIVED IN FERRULE
The grinding apparatuses proposed in these patents and patent application are of the type in which the end surfaces of the optical fibers to be ground are pressed against the grinding plate, and a synthetic relative movement having a rotational component (rotation about fixed axis) and a revolution component (revolution along an orbit) is caused between the grinding plate and the optical fiber end surfaces, thereby grinding these end surfaces.
FIG. 4 is a plan view of a grinding holder of a known apparatus for grinding end surfaces of a plurality of optical fibers. The grinding holder has a holder plate capable of holding fiber end devices of different types one of which is illustrated in sectional view in FIG. 5.
The holder plate 1 is provided at its center with a cylindrical hub 2 for receiving a holder shaft. The holder plate 1 is further provided with a plurality of mounting members 3 which are designed to mount fiber end devices of the same configuration. These mounting members are arranged on a circle E shown by a chain line and concentric with the holder plate 1.
More specifically, FIG. 5 is a sectional view taken along the line V--V of FIG. 4, and the mounting member 3 shown therein is adapted to mount an FC-type ferrule 5 which receives an end of an optical fiber 4. The end surface of an optical fiber 4 exposed from the ferrule 5, is to be ground perpendicularly to the axis of the optical fiber.
To explain in more detail, a plurality of through-holes 7 are formed on the above-mentioned circle E. A ferrule receiving sleeve 8 for receiving the ferrule 5 is press-fit in each hole 7. Namely, the ferrule receiving sleeve 8 has a through bore for receiving the ferrule 5 and is externally threaded at 8a. A nut 9 has a slit 10 and is internally threaded so as to be screwed to the above-mentioned external thread 8a thereby fixing the FC-type ferrule 5.
The end surfaces 6 of the FC-type ferrules 5 are pressed against a grinding plate 11, and a relative movement based on a circular path is caused to occur between the end surfaces of the ferrules 5 and the grinding plate 11, so that the end surfaces of six optical fibers are simultaneously ground.
Nowadays, various types of optical fiber connectors are used, such as FC type, SC type, ST.sup.R type, DIN type, MT type and so forth. Furthermore, these connectors are grouped according to the shape in which the ferrule end is ground, e.g., spherical surface with vertical axis, spherical surface inclined with respect to vertical plane, and so forth. Thus, more than 20, almost 30 types of optical fiber connectors exist according to the combination of the connector type and the shape of grinding, requiring different specifications or types of grinding work. Hitherto, different types of grinding holder plates have had to be prepared and used, adapted to each of the variety of types of the optical fiber end devices of different designs.
The grinding holder plate is one of the most critical components of the grinding apparatus, since it controls the precision of grinding of the optical fiber end surfaces. In general, therefore, a grinding holder plate has to be finished with a high degree of precision on the order of 1 .mu.m. Thus, the grinding holder plate is one of the most expensive components. It may be not so difficult to prepare many different types of holder plates in a factory where limited types of fiber end devices are to be ground in large quantities. However, a difficulty is encountered at sites where a variety of types of fiber end devices have to be ground in small lots. Obviously, preparation and use of many different grinding holder plates at each of sites is disadvantageous from the view points of cost, transportation and administration. This has given a rise to the demand for an optical fiber end surface grinding apparatus in which a single grinding holder plate can be adapted to a variety of types of optical fibers.